We use a plate to block the air scatter. The plate is directly over the sample (perpendicular to the sample), parallel to the G axis. The lower side of the plate is a couple to a few mm above the sample. As theta goes up, the reflecting area of the sample decreases. This may decrease the concern that the sample is largely out of the focusing circle at high angle when the div angle is large. Therefore it has a constant reflecting area at lower angle and a decreasing reflecting area at high angle when the variable slits are used.
With BGMN, this can described with a statement: Length-equatorial = Lesser of (20 or whatever mm, or calculated length with the known geometry). (Please refer to BGMN.de for keywords and syntax). Seems hard to find a place to put in free-style statement in other programs. Cheers Jilin zhang
